1. Field of the Invention
The invention relates to a method and a device for operating a tank ventilation system, and to a tank ventilation system.
2. Description of Prior Art
It is known to equip vehicles, in particular motor vehicles, with tank ventilation systems to avoid evaporation of hydrocarbons from the fuel tank into the atmosphere. In order to adsorb the hydrocarbon vapors, the tank ventilation systems are frequently equipped with an activated carbon filter. Such activated carbon filters can only absorb a limited quantity of hydrocarbons and have to be regenerated, that is to say cleaned, when a certain degree of saturation is reached. The activated carbon filter can therefore serve as a buffer for the hydrocarbons released from the fuel, as a result of which the hydrocarbons released from the fuel can be fed in a predefined fashion for combustion in an internal combustion engine.
DE 10 2007 002 188 A1 discloses a tank ventilation system for a hybrid vehicle, wherein the tank ventilation system comprises at least a fuel tank and a suction line leading from a regeneratable filter device to an intake section of the internal combustion engine. A control device is provided that can actuate various valve devices to purge the filter device, with the result that ambient air can be fed to the internal combustion engine through the filter device and the suction line. The control device is also embodied in such a way that in a pure electric operating mode of the hybrid vehicle it activates the internal combustion engine as a function of a load state of the filter device or purge gas concentration.
US 2005/0211228 A1 discloses a fuel vapor treatment system for an internal combustion engine. A pump generates a gas flow within a measuring passage that has a throttle orifice. A difference pressure sensor detects a pressure difference between the two ends of the throttle orifice. Switching valves are arranged in the measuring passage to generate a first concentration measuring state in which the measuring passage is opened at its two ends and in which the gas flowing through the measuring passage is the atmosphere, and to generate a second concentration measuring state in which the measuring passage is connected at its two ends to a container and in which the gas flowing through the measuring passage is a fuel vapor which is an air/fuel mixture provided by the container. An ECU calculates a fuel vapor concentration on the basis of a pressure difference detected in the first concentration measuring state and a pressure difference detected in the second concentration measuring state.